A novel fluorescent-tagged scale inhibitor, maleic anhydride-oxalic acid-allypolyethoxy carboxylate-8-hydroxy-1,3,6-pyrene trisulfonic acid trisodium salt (pyranine) (MA-APEM-APTA) was synthesized by maleic anhydride (MA), oxalic acid-allypolyethoxy carboxylate (APEM) and 8-hydroxy-1,3,6-pyrene trisulfonic acid trisodium salt (APTA). Structures of APTA. APEM, and MA-APEM-APTA were carried out by FT-IR and H-1 NMR. The observation shows that the dosage of MA-APEM-APTA plays an important role on CaCO3 inhibition. It can be concluded that the order of preventing the precipitation from flask tests was MA-APEM > MA-APEM-APTA > T225 > PESA > PAA HPMA. Relationship between MA-APEM-APTA's fluorescent intensity and its dosage was studied. Correlation coefficient R-2 of MA-APEM-APTA's is 0.9973. The effect on formation of CaCO3 was investigated with combination of scanning electronic microscopy (SEM), transmission electron microscope (TEM), X-ray powder diffraction (XRD) and FT-IR analysis. MA-APEM-APTA can be used to accurately measure copolymer consumption on line besides providing excellent CaCO3. (C) 2014 Elsevier B.V. All rights reserved.